diff --git a/src/stores/useModelStore.ts b/src/stores/useModelStore.ts
index 2a4b883..d469a08 100644
--- a/src/stores/useModelStore.ts
+++ b/src/stores/useModelStore.ts
@@ -1,5 +1,26 @@
 import { create } from 'zustand';
 
+export interface ScaleRatio {
+  label: string;     // e.g. "1:50", "2:1", "1:1"
+  factor: number;    // render multiplier: 1:50 => 0.02, 2:1 => 2, 1:1 => 1
+}
+
+export const SCALE_PRESETS: ScaleRatio[] = [
+  { label: '10:1',  factor: 10 },
+  { label: '4:1',   factor: 4 },
+  { label: '2:1',   factor: 2 },
+  { label: '1:1',   factor: 1 },
+  { label: '1:2',   factor: 1 / 2 },
+  { label: '1:4',   factor: 1 / 4 },
+  { label: '1:8',   factor: 1 / 8 },
+  { label: '1:10',  factor: 1 / 10 },
+  { label: '1:20',  factor: 1 / 20 },
+  { label: '1:33',  factor: 1 / 33 },
+  { label: '1:50',  factor: 1 / 50 },
+  { label: '1:100', factor: 1 / 100 },
+  { label: '1:200', factor: 1 / 200 },
+];
+
 interface ModelInfo {
   fileName: string;
   fileSize: number;